Synchronous motor control method

ABSTRACT

It is determined which of six continuous sections having different magnitude correlation of signal amplitude of each phase of an input three-phase signal a section is. Predetermined subtraction is performed between respective phases in the section, to obtain a normalized amplitude value normalized in the section, using the subtraction result. The normalized amplitude value is converted to a vector phase for one cycle based on a predetermined phase and output corresponding to the determined section.

RELATED APPLICATIONS

This application is a Divisional of U.S. patent application Ser. No.12/010,021, filed on Jan. 18, 2008, now U.S. Pat. No. 7,839,114 claimingpriority of Japanese Patent Application No. 2007-029620, filed on Feb.8, 2007, the entire contents of each of which are hereby incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a phase detection method and a phasedetecting apparatus capable of detecting phases of a plurality of phasesignals on a real time basis, and also to a control method and asynchronous motor controller for performing sensorless synchronouscontrol of the synchronous motor using the same.

2. Description of the Related Art

A typical synchronous motor controller includes an alternating currentdetector that detects electric current of a motor provided in one offeed lines from an inverter circuit to the motor, a motor-current-phasedetector that detects a motor current phase on the basis of a motorvoltage phase at the time of zero crossing of the current, and acalculating unit that calculates a voltage command or frequency commandof the inverter circuit so that the motor current phase is same as adesired motor current phase. The inverter circuit is then controlledbased on the calculation result. A conventional synchronous motorcontroller has been disclosed in Japanese Patent Application Laid-openNo. H5-236789.

Moreover, technique of sensorless synchronous control of the synchronousmotor is available. For example, in the method disclosed in JapanesePatent Application Laid-open No. 2006-223085, the position of a rotor isestimated based on a voltage equation for the motor. In this method,however, a highly accurate motor constant is required, and complicatedcontrol needs to be performed.

In the technique disclosed in Japanese Patent Application Laid-open No.H5-236789, a phase difference between the motor current phase and themotor voltage phase is detected at the time of zero-crossing of current,i.e., phase detection is performed for every 180°. Phase detection forevery 180°, however, leads to poor detection accuracy, moreover it isnot possible to detect instantaneous phase.

Generally, when the phase difference is detected on the real time basis,a three-phase signal is converted to a two-phase signal to obtain avector phase. For example, when three-phase to two-phase conversion isperformed with respect to the three-phase signal shown in the upper partof FIG. 1, waveforms of a real axis component and an imaginary axiscomponent are obtained as shown in the upper part of FIG. 4. When arctantransform is performed using the real axis component and the imaginaryaxis component, as shown in the lower part of FIG. 4, a vector phase isobtained. In this conventional method, however, processing to obtain thedetection result is complicated, and when phase detection is performedon the real time basis, a device having a large computing capacity isrequired.

Japanese Patent Application Laid-open No. 2004-336876 discloses atechnique with which it is possible to detect the phase at an arbitrarytiming. Even this method is a method for detecting discreteinstantaneous phase, and therefore the detection accuracy is poor andphase detection cannot be performed on the real time basis.

SUMMARY OF THE INVENTION

It is an object of the present invention to at least partially solve theproblems in the conventional technology.

According to an aspect of the present invention, there is provided aphase detection method including determining which of a plurality ofcontinuous sections having different magnitude correlation of signalamplitude of each phase a section is, based on an input signal amplitudevalue of a plurality of phases; normalizing including performingpredetermined subtraction with respect to the signal amplitude betweenrespective phases for each section determined at the determining, toobtain a normalized amplitude value normalized in the section, using thesubtraction result; and outputting including converting the normalizedamplitude value obtained at the normalizing to a vector phase for onecycle based on a predetermined phase, and outputting the vector phasecorresponding to the section determined at the determining.

According to another aspect of the present invention, there is provideda phase detection method including determining which of six continuoussections, first to sixth sections, in which magnitude correlation of asignal amplitude value of an input three-phase signal of R-phase,S-phase, and T-phase takes a R-phase value>T-phase value>S-phase value,a R-phase value>S-phase value>T-phase value, a S-phase value>R-phasevalue>T-phase value, a S-phase value>T-phase value>R-phase value, aT-phase value>S-phase value>R-phase value, and a T-phase value>R-phasevalue>S-phase value, the section is; calculating the first section by((R-phase value)−(T-phase value))/((R-phase value)−(S-phase value)), thesecond section by ((S-phase value)−(T-phase value))/((R-phasevalue)−(T-phase value)), the third section by ((S-phase value)−(R-phasevalue))/((S-phase value)−(T-phase value)), the fourth section by((T-phase value)−(R-phase value))/((S-phase value)−(R-phase value)), thefifth section by ((T-phase value)−(S-phase value))/((T-phasevalue)−(R-phase value)), the sixth section by ((R-phase value)−(S-phasevalue))/((T-phase value)−(S-phase value)), to obtain a normalizedamplitude value normalized in each section; and second outputtingincluding multiplying the normalized amplitude value of the first to thesixth sections, respectively, by a phase of 60°, to calculate a phasevalue by adding phases of 30°, 90°, 150°, 210°, 270°, and 330°,respectively, to the multiplied values of the first to the sixthsections, and when the phase value of the sixth section is equal to orlarger than 360°, obtaining a phase value by subtracting the phase of360° from the phase value, and outputting a vector phase for one cycle.

According to still another aspect of the present invention, there isprovided a phase detecting apparatus including a section determiningunit that determines which of a plurality of continuous sections havingdifferent magnitude correlation of signal amplitude of each phase asection is, based on an input signal amplitude value of a plurality ofphases; an amplitude normalizing unit that performs predeterminedsubtraction with respect to the signal amplitude between respectivephases for each section determined by the section determining unit, toobtain a normalized amplitude value normalized in the section, using thesubtraction result; and a phase outputting unit that converts thenormalized amplitude value obtained by the amplitude normalizing unit toa vector phase for one cycle based on a predetermined phase, and outputsthe vector phase corresponding to the section determined by the sectiondetermining unit.

According to still another aspect of the present invention, there isprovided a phase detecting apparatus including a section determiningunit that determines which of six continuous sections, first to sixthsections, in which magnitude correlation of a signal amplitude value ofan input three-phase signal of R-phase, S-phase, and T-phase takes aR-phase value>T-phase value>S-phase value, a R-phase value>S-phasevalue>T-phase value, a S-phase value>R-phase value>T-phase value, aS-phase value>T-phase value>R-phase value, a T-phase value>S-phasevalue>R-phase value, and a T-phase value>R-phase value>S-phase value,the section is; an amplitude normalizing unit that calculates the firstsection by ((R-phase value)−(T-phase value))/((R-phase value)−(S-phasevalue)), the second section by ((S-phase value)−(T-phasevalue))/((R-phase value)−(T-phase value)), the third section by((S-phase value)−(R-phase value))/((S-phase value)−(T-phase value)), thefourth section by ((T-phase value)−(R-phase value))/((S-phasevalue)−(R-phase value)), the fifth section by ((T-phase value)−(S-phasevalue))/((T-phase value)−(R-phase value)), the sixth section by((R-phase value)−(S-phase value))/((T-phase value)−(S-phase value)), toobtain a normalized amplitude value normalized in each section; and aphase outputting unit that multiplies the normalized amplitude value ofthe first to the sixth sections, respectively, by a phase of 60°, tocalculate a phase value by adding phases of 30°, 90°, 150°, 210°, 270°,and 330°, respectively, to the multiplied values of the first to thesixth sections, and when the phase value of the sixth section is equalto or larger than 360°, obtains a phase value by subtracting the phaseof 360° from the phase value, and outputs a vector phase for one cycle.

According to still another aspect of the present invention, there isprovided a synchronous-motor control method including calculating avoltage vector phase and a current vector phase to be applied to thesynchronous motor based on the above phase detection method, tocalculate a power factor, which is a phase difference between thevoltage vector phase and the current vector phase on a real time basis;and controlling the synchronous motor based on the power factor.

According to still another aspect of the present invention, there isprovided a synchronous motor controller including a voltage phasedetector that acquires a vector phase of voltage to be applied to asynchronous motor by the above phase detecting apparatus; a currentphase detector that obtains a vector phase of current to be applied tothe synchronous motor by the above phase detecting apparatus; a powerfactor calculator that calculates a power factor, which is a phasedifference between the voltage vector phase detected by the voltagephase detector and the current vector phase detected by the currentphase detector, on a real time basis; and a control unit that performssynchronous control on the synchronous motor based on the power factorobtained by the power factor calculator.

According to still another aspect of the present invention, there isprovided a synchronous motor controller including a current phasedetector that acquires a vector phase of current to be applied to thesynchronous motor by the above phase detecting apparatus; a power factorcalculator that calculates a power factor, which is a phase differencebetween a voltage vector phase and the current vector phase detected bythe current phase detector, on a real time basis; and a control unitthat performs synchronous control with respect to the synchronous motorbased on the power factor obtained by the power factor calculator. Thevoltage vector phase to be input to the power factor calculator iscontrolled by the control unit, so that the phase is a phase of avoltage drive signal for generating an AC signal to be applied to thesynchronous motor.

The above and other objects, features, advantages and technical andindustrial significance of this invention will be better understood byreading the following detailed description of presently preferredembodiments of the invention, when considered in connection with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram for explaining a concept of a phasedetection method according to a first embodiment of the presentinvention;

FIG. 2 is a schematic diagram for explaining another concept of thephase detection method according to the first embodiment;

FIGS. 3A and 3B depict a relationship between a phase and an errordetected by the phase detection method according to the firstembodiment;

FIG. 4 is a schematic diagram for explaining calculation of a vectorphase by performing arctan transform using a real axis component and animaginary axis component obtained by a three-phase to two-phaseconversion;

FIG. 5 is a circuit diagram of the configuration of a phase detectingapparatus according to the first embodiment;

FIG. 6 is a circuit diagram of the configuration of a modification ofthe phase detecting apparatus according to the first embodiment;

FIG. 7 is a flowchart of a phase detection method according to a secondembodiment of the present invention;

FIG. 8 is a flowchart of a phase detection method according to amodification of the second embodiment;

FIG. 9 depicts a relationship between voltage and current on arotational coordinate system;

FIG. 10 depicts a relationship among voltage fluctuation, currentfluctuation, and phase difference fluctuation on the rotationalcoordinate system;

FIG. 11 is a block diagram of a synchronous motor controller accordingto a third embodiment of the present invention;

FIG. 12 is a block diagram of a first modification of the synchronousmotor controller according to the third embodiment;

FIG. 13 is a block diagram of a second modification of the synchronousmotor controller according to the third embodiment;

FIG. 14 is a block diagram of a third modification of the synchronousmotor controller according to the third embodiment;

FIG. 15 depicts a relationship between a torque and a power factor, atwhich power consumption efficiency becomes the largest; and

FIG. 16 is a block diagram of a synchronous motor controller accordingto a fourth embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Exemplary embodiments of the present invention will be explained belowin detail with reference to the accompanying drawings.

FIGS. 1 and 2 depict a concept of a phase detection method according toa first embodiment of the present invention. An upper part of FIG. 1depicts three phase signals of R-phase, S-phase, and T-phase. Thesignals can be voltage signals or current signals. There are six regionsin which magnitude correlation of the signals of the respective phasesis different. As the phase proceeds, the sequence of R-phasesignal>T-phase signal>S-phase signal, R-phase signal>S-phasesignal>T-phase signal, S-phase signal>R-phase signal>T-phase signal,S-phase signal>T-phase signal>R-phase signal, T-phase signal>S-phasesignal>R-phase signal, and T-phase signal>R-phase signal>S-phase signalis repeated. The variation of the magnitude correlation occurs everytime the phase proceeds by 60°, and the magnitude correlation changes ata point where any two of the three phase signals intersect.

When it is assumed that these six regions are respectively sections “0”to “5”, the phase of the three-phase signals corresponding to eachsection is, as shown in the middle part of FIG. 1, 30° to 90° in section“0”, 90° to 150° in section “1”, 150° to 210° in section “2”, 210° to270° in section “3”, 270° to 330° in section “4”, 330° to 360° and 0° to30° in section “5”.

When watching respective sections closely, for example, as T-phase insection “0”, the value of the intermediate phase has an approximatelylinear waveform change with respect to the phase change. The phasechange can be obtained as an approximate value from the change of thevalue of the intermediate phase. However, because the value of theintermediate phase changes with an amplitude change of the three phases,the approximate value of the phase cannot be obtained by the valueitself of the intermediate phase.

In the first embodiment, as shown in the lower part of FIG. 1, a firstsubtraction process for subtracting the smallest phase value from thelargest phase value in each section, and a second subtraction processfor subtracting the intermediate phase value from the largest phasevalue in sections “0”, “2”, and “4”, and subtracting the smallest phasevalue from the intermediate phase value in sections “1”, “3”, and “5”are performed. A result of the second subtraction process has anapproximately linear relationship with respect to the phase change, anda result of the first subtraction process has less change with respectto the phase change. For example, as shown in the lower part of FIG. 1,the result of the second subtraction process subtracting the T-phasevalue from the R-phase value has substantially a linear characteristicwith respect to the phase change, and the result of the firstsubtraction process subtracting the S-phase value from the R-phase valuehas a flat characteristic having less change with respect to the phasechange, in section “0”.

Thereafter, a normalization process is performed in which the secondsubtraction result is divided by the first subtraction result for eachsection. For example, in section “0”, the normalization process isperformed by performing the division ((R-phase value)−(T-phasevalue))/((R-phase value)−(S-phase value)). As a result, as shown in themiddle part of FIG. 2, each section has a normalized value, whichchanges substantially linearly from 0 to 1 with respect to the phasechange and does not depend on the amplitude of three phases.

Because the phase width of each section is 60°, the normalized value ismultiplied by 60 for each section, and a converted phase value iscalculated for each section “0” to “5” by adding the phase 30°, 90°,150°, 210°, 270°, 330° to the multiplied value, respectively. When thephase value of section “5” is equal to or larger than 360°, a convertedphase value is calculated by subtracting the phase 360° from the phasevalue, thereby calculating a vector phase of one cycle. As a result, asshown in the lower part of FIG. 2, a vector phase that changessubstantially linearly at 360° with respect to the phase change can beobtained.

The specifically obtained converted phase value for every 1° in section“0” (30° to 90°) is as shown in FIGS. 3A and 3B. For example, as shownin FIG. 4, an error between a true phase value obtained by performing anarctan operation and the converted phase value obtained in the firstembodiment is as small as approximately less than 1.1°. Likewise inother sections, the accuracy is approximately less than 1.1°.Accordingly, the vector phase can be easily obtained at high accuracyover the whole sections.

A phase detecting apparatus that embodies the phase detection method isexplained next. FIG. 5 is a circuit diagram of the configuration of thephase detecting apparatus according to the first embodiment. As shown inFIG. 5, the phase detecting apparatus includes a three-phase signalsource 1, a section determination circuit 100, a subtraction circuit101, a normalization circuit 102, and a converted-phase output circuit103.

The three-phase signal source 1 outputs three phase signals of R-phase,S-phase, and T-phase. The section determination circuit 100 determinesto which of the six sections “0” to “5” the signals belong, based onmagnitude correlation of R-phase, S-phase, and T-phase, and outputs thedetermination result. The section determination circuit 100 includescomparators 2 to 4, and each of the comparators 2 to 4 output “1” whenR-phase value>S-phase value, when S-phase value>T-phase value, and whenT-phase value>R-phase value. NOT elements 5 to 7 branch-connected to theoutput of the comparators 2 to 4 output “1”, respectively, when R-phasevalue<S-phase value, when S-phase value<T-phase value, and when T-phasevalue<R-phase value. The outputs of each of the comparators 2 to 4 andNOT elements 5 to 7 are connected to AND elements 8 to 13. The outputsof the NOT elements 6 and 7 are input to the AND element 8, and the ANDelement 8 outputs “1” when R-phase value>T-phase value>S-phase value,that is in section “0”. The outputs of the comparators 2 and 3 are inputto the AND element 9, and the AND element 9 outputs “1” when R-phasevalue>S-phase value>T-phase value, that is in section “1”. The outputsof the NOT elements 5 and 7 are input to the AND element 10, and the ANDelement 10 outputs “1” when S-phase value>R-phase value>T-phase value,that is in section “2”. The outputs of the comparators 3 and 4 are inputto the AND element 11, and the AND element 11 outputs “1” when S-phasevalue>T-phase value>R-phase value, that is in section “3”. The outputsof the NOT elements 5 and 6 are input to the AND element 12, and the ANDelement 12 outputs “1” when T-phase value>S-phase value>R-phase value,that is in section “4”. The outputs of the comparators 2 and 4 are inputto the AND element 13, and the AND element 13 outputs “1” when T-phasevalue>R-phase value>S-phase value, that is in section “5”.

The subtraction circuit 101 performs the subtraction process explainedabove with reference to the lower part of FIG. 1 or the upper part ofFIG. 2. That is, the subtraction circuit 101 includes subtracters 14 to16 that perform subtractions ((R-phase value)−(S-phase value)),((S-phase value)−(T-phase value)), and ((T-phase value)−(R-phasevalue)), respectively. Polarity inverters 17 to 19 branch-connected torespective subtracters 14 to 16 multiply the outputs of the subtracters14 to 16 by (−1), respectively, and output ((S-phase value)−(R-phasevalue)), ((T-phase value)−(S-phase value)), and ((R-phasevalue)−(T-phase value)). Multipliers 20, 21, 22, 23, 24, 25, 26, 27, 28,29, 30, and 31 respectively output the first subtraction result and thesecond subtraction result corresponding to sections “0” to “5” to thenormalization circuit 102. Specifically, multipliers 20 to 31 multiplythe values of the respective subtracters 14 to 16 and the polarityinverters 17 to 19 by the output from the section determination circuit100, and output the first subtraction result and the second subtractionresult only corresponding to sections “0” to “5”, for which “1” isoutput from the section determination circuit, to the normalizationcircuit 102. For example, in the case of section “0”, ((R-phasevalue)−(S-phase value)) is output from the multiplier 20, ((R-phasevalue)−(T-phase value)) is output from the multiplier 21, and nothing isoutput from other multipliers 22 to 31.

The normalization circuit 102 performs an amplitude normalizationprocess shown in the middle part of FIG. 2. The normalization circuit102 has adders 32 to 37. The adders 32 to 37 have a function forbranch-outputting a denominator and a numerator of division, which is anormalization operation, and adders 32 to 34 output the denominator, andadders 35 to 37 output the numerator. A divider 38 divides the valuebranch-output on the numerator side by the value branch-output on thedenominator side, and outputs a result thereof to the converted-phaseoutput circuit 103 as a normalized amplitude value A. For example, insection “0”, ((R-phase value)−(S-phase value)) output from themultiplier 20 is input to the denominator side of the divider 38 via theadders 32 and 34, and ((R-phase value)−(T-phase value)) output from themultiplier 21 is input to the numerator side of the divider 38 via theadders 35 and 37, thereby performing an amplitude normalizationoperation of section “0”.

The converted-phase output circuit 103 outputs the converted phase valueshown in the lower part of FIG. 2. A multiplier 39 multiplies thenormalized value output from the normalization circuit 102 by 60 andoutputs the result thereof to an adder 49. On the other hand, outputs ofthe AND elements 8 to 13 in the section determination circuit 100 arerespectively input to multipliers 40 to 45. When “1” is output fromrespective AND elements 8 to 13, values of 30, 90, 150, 210, 270, and330 are output to the adder 49 via the adders 46 to 48. The adder 49adds the value output from the multiplier 39 and the value output fromany one of the multipliers 40 to 45, and outputs the result thereof as aconverted phase value B, which is the vector phase. A comparator 50branch-connected to the adder 49 compares the output of the adder 49with 360 to determine whether the output of the adder 49 is above 360.When the output of the adder 49 is above 360, the comparator 50 outputs“1” to a multiplier 51, and the multiplier 51 multiplies “1” by 360, andoutputs (−360) to an adder 52 to be added. A value obtained bysubtracting 360 from the value output from the adder 49 is output as theconverted phase value B. That is, the converted phase value B in section“5” is output.

In the first embodiment, the vector phase can be obtained on the realtime basis with a simple configuration, with accuracy as high as anerror from the true vector phase value being within approximately 1.1°.

As shown in FIG. 6, a correcting unit 104 that performs phase correctionwith respect to the converted phase value B can be added to theconfiguration shown in FIG. 5. Specifically, a correction table in whicha relationship between the converted phase value and the error shown inFIGS. 3A and 3B is stored is provided for all sections, and thecorrecting unit 104 performs addition and subtraction to eliminate theerror. Consequently, a linear characteristic of the phase can be ensuredin each section, thereby enabling highly accurate detection of thevector phase. Further, when the correction table is used, in the case ofa value between values stored in the correction table, interpolation canbe performed.

In the second subtraction, the intermediate phase value is subtractedfrom the largest phase value in sections “0”, “2”, and “4”, and thesmallest phase value is subtracted from the intermediate phase value insections “1”, “3”, and “5”. However, subtraction in “0”, “2”, and “4”and subtraction in sections “1”, “3”, and “5” can be reversed. That is,the smallest phase value is subtracted from the intermediate phase valuein sections “0”, “2”, and “4”, and the intermediate phase value issubtracted from the largest phase value in sections “1”, “3”, and “5”.In this case, the converted phase value can be output, for example, bysubtracting the second calculation result from 1.

An explanation has been given about with three phase signals, however,the number of phase signals is not limited to three. In other words, aplurality of phase signals can be employed. In this case, division ofsections can be performed at a position where two phase signalsintersect with each other, and subtraction capable of obtaining thelinear characteristic and subtraction capable of obtaining thesubstantially flat characteristic in each section can be performed toobtain the normalized value.

A second embodiment of the present invention is explained next. In thefirst embodiment, the phase detecting apparatus is constructed byhardware. In the second embodiment, however, the phase detection methoddescribed in the first embodiment is realized by software. The softwareis stored as a computer program in a read only memory (ROM) or randomaccess memory (RAM), read and executed by a central processing unit(CPU), and realized by a microcomputer or the like.

FIG. 7 is a flowchart of the phase detection method according to thesecond embodiment. To begin with, values of R-phase, S-phase, andT-phase of three-phase signal source 1 are read (step S101), and sixmagnitude correlations are determined based on the read three values(step S102).

In the case of magnitude correlation (section “0”) of R-phasevalue>T-phase value>S-phase value, a normalized amplitude valueP0=(R−T)/(R−S) is obtained (step S103), a converted phase valuePh=30+P0×60 is obtained (step S104), and the obtained converted phasevalue Ph is output as the vector phase.

In the case of magnitude correlation (section “1”) of R-phasevalue>S-phase value>T-phase value, a normalized amplitude valueP1=(S−T)/(R−T) is obtained (step S105), a converted phase valuePh=90+P1×60 is obtained (step S106), and the obtained converted phasevalue Ph is output as the vector phase.

In the case of the magnitude correlation (section “2”) of S-phasevalue>R-phase value>T-phase value, a normalized amplitude valueP2=(S−R)/(S−T) is obtained (step S107), a converted phase valuePh=150+P2×60 is obtained (step S108), and the obtained converted phasevalue Ph is output as the vector phase.

In the case of magnitude correlation (section “3”) of S-phasevalue>T-phase value>R-phase value, a normalized amplitude valueP3=(T−R)/(S−R) is obtained (step S109), a converted phase valuePh=210+P3×60 is obtained (step S110), and the obtained converted phasevalue Ph is output as the vector phase.

In the case of magnitude correlation (section “4”) of T-phasevalue>S-phase value>R-phase value, a normalized amplitude valueP4=(T−S)/(T−R) is obtained (step S111), a converted phase valuePh=270+P4×60 is obtained (step S112), and the obtained converted phasevalue Ph is output as the vector phase.

In the case of magnitude correlation (section “5”) of T-phasevalue>R-phase value>S-phase value, a normalized amplitude valueP5=(R−S)/(T−S) is obtained (step S113), a converted phase valuePh=330+P5×60 is obtained (step S114). It is determined whether theobtained converted phase value Ph is equal to or larger than 360 (stepS115). When the obtained converted phase value Ph is equal to or largerthan 360, 360 is subtracted from the converted phase value Ph (stepS116) to output the subtracted converted phase value Ph as the vectorphase. When the obtained converted phase value Ph is less than 360, theconverted phase value Ph is output as the vector phase.

As shown in FIG. 8, a correction process for correcting an error of theconverted phase value Ph obtained by the process procedure shown in FIG.7 can be performed (step S201), to output the corrected value as thevector phase. The correction process is performed using the correctiontable as in the correcting unit 104 shown in FIG. 6. Accordingly, highlyaccurately phase detection can be performed on the real time basis witha simple configuration.

A third embodiment of the present invention is explained next. The thirdembodiment realizes a synchronous motor controller using the phasedetecting apparatus or the phase detection method described in the firstand second embodiments.

The synchronous motor during a synchronous operation, for example, apermanent-magnet (PM) motor is explained. FIG. 9 is a vector diagram ofinduced voltage, current, and voltage in a rotational coordinate systemof the PM motor during a synchronous operation. Ld denotes d-axisreactance, Lq denotes q-axis reactance, Φ denotes an induced voltageconstant of the motor, I denotes current, and V denotes voltage. φIdenotes current phase, φV denotes voltage phase, φpf denotes a phasedifference between current and voltage and expresses a power factor.Applied torque is denoted as T.

With reference to FIG. 9, because φI=arctan (Iq/Id), andφV=arctan((Φ+LdId)/LqIq), following relations exist:φpf=φV−φI=arctan((Φ+LdId)/LqIq)−arctan(Iq/Id)  (1)V=ω((Φ+LdId)/LqIq)²+(LqIq)²)^(1/2)  (2)T=ΦIq+(Ld−Lq)IdIq (where T is torque)  (3)If Equations (1) to (3) are established continuously and simultaneouslyduring an operation, synchronization also continues. During theoperation, torque T is determined according to a load, however, it isconstant in a short period of time. An angular frequency ω is alsoconstant in a short period of time. If it is assumed here that the powerfactor φpf is constant, Id and Iq are uniquely determined according toEquations (1) and (3), and magnitude of voltage V is uniquelydetermined. Accordingly, if voltage V can be controlled so that Equation(2) is established with respect to the power factor φpf, Equations (1)and (3) can be established during the operation, and synchronization ofthe operation continues.

The vector diagram shown in FIG. 9 is a rotational coordinate system.However, because the power factor φpf is a relative phase differencebetween voltage and current, it does need not to be a phase differenceof the rotational coordinate system, and can be detected similarly by afixed coordinate system. The magnitude of voltage V can be also detectedby the fixed coordinate system, because it is invariable in therotational coordinate system and the fixed coordinate system.

Therefore, synchronization of the operation is enabled by controllingthe amplitude of voltage based on the power factor detected by the fixedcoordinate system. That is, a sensorless synchronous operation isenabled without requiring position detection.

The control method of the synchronous motor according to the phasedifference of the voltage amplitude is explained here. FIG. 10 is aschematic diagram for explaining a relationship between voltage changeand phase difference change between current and voltage in a simplifiedmanner. In FIG. 10, when torque T is constant, Iq is considered to besubstantially constant, and a terminal point of a vector of current Imoves parallel with axis d. On the other hand, a terminal point of avector of voltage V moves vertical to axis q. The direction is such thatas the terminal point of the vector of current I moves from right toleft in the drawing, the terminal point of the vector of voltage V movesfrom above downward in the drawing. At this time, the amplitude ofvoltage V decreases.

On the other hand, when a vector phase change of voltage V is comparedwith a vector phase change of current I, a phase change in current I islarger than that in voltage V, and as shown in FIG. 10, the phasedifference decreases, changing from phase difference φpfa to phasedifference φpfb. That is, a relationship between the amplitude ofvoltage V and the phase difference φpf is such that when the amplitudeof voltage V is increased, the phase difference φpf also increases, andwhen the amplitude of voltage V is decreased, the phase difference φpfalso decreases. Therefore, if the amplitude of voltage V with respect tothe phase difference φpf is controlled by the relationship between theamplitude of voltage V and the phase difference φpf, Equations (1) to(3) can be satisfied.

As a result, when the phase difference φpf is to be increased, theamplitude of voltage V is increased, and when the phase difference φpfis to be decreased, the amplitude of voltage V is decreased, therebysatisfying Equations (1) to (3) and enabling synchronous control of thesynchronous motor (first control method).

When the load abruptly changes or when speed control is being performed,time is required until Equations (1) to (3) are established only by theamplitude control of voltage V, thereby causing an unstable state.Therefore, the phase difference φpf until Equations (1) to (3) areestablished needs to be stabilized, and therefore it is desired todirectly control the voltage phase so that a change of the phasedifference φpf is hindered, by feeding back the change of the phasedifference φpf (second control method).

Further, the relationship between the amplitude of voltage V and thephase difference φpf for establishing Equations (1) to (3) depends onthe torque and angular velocity. Therefore, it is preferable to change again of a regulator according to the torque and the angular velocity asthe optimum regulated gain (third control method).

By the first to the third control methods, sensorless synchronouscontrol of the synchronous motor can be stably performed with highaccuracy at the time of startup, at the time of load fluctuation, and atthe time of velocity control.

FIG. 11 is a block diagram of the configuration of a synchronous motorcontroller according to the third embodiment. The synchronous motorcontroller is a so-called inverter. Switching elements 202 to 207constitute a bridge circuit, and the respective switching elements 202to 207 are driven and controlled by a drive circuit 213 to convert an DCinput from a DC power source 201 to a three-phase AC signal, and thethree-phase AC signal is supplied as an AC power supply of a synchronousmotor 211. The synchronous motor 211 drives a load 212.

A voltage detector 214 detects a three-phase voltage amplitude valuefrom an input port to the synchronous motor 211 of the three-phase ACsignal output from the bridge circuit. A voltage phase calculator 215calculates voltage phase φV, which is the vector phase of the voltage,based on the three-phase voltage amplitude value. On the other hand,current detectors 208 to 210 are provided at the input port of thesynchronous motor 211 to detect a three-phase current amplitude value. Acurrent phase calculator 216 calculates current phase φI, which is thevector phase of the current, based on the three-phase current amplitudevalue detected by the current detectors 208 to 210. The voltage phasecalculator 215 and the current phase calculator 216 are realized by thephase detecting apparatus or a device using the phase detection methoddescribed in the first and second embodiments. The voltage phasecalculator 215 and the current phase calculator 216 can be realized bythe circuit described in the first embodiment or can be realized by thesoftware described in the second embodiment. In any case, the voltagephase calculator 215 and the current phase calculator 216 can detect thevoltage phase φV and the current phase φI highly accurately on the realtime basis with a simple configuration.

While the voltage phase φV and the current phase φI shown in FIGS. 9 and10 are the phase in the rotational coordinate system, the voltage phaseφV and the current phase φI respectively calculated by the voltage phasecalculator 215 and the current phase calculator 216 are the phase forcalculating a phase difference φpf, which need not be the phase on therotational coordinate, and are the phase calculation result on the fixedcoordinate.

A power factor calculator 217 calculates the power factor φpf, which isa phase difference between the voltage phase φV and the current phase φIrespectively output from the voltage phase calculator 215 and thecurrent phase calculator 216, to output the power factor φpf to asubtracter 220. On the other hand, a target-power-factor setting unit218 outputs a set target value of the power factor to the subtracter220. The subtracter 220 outputs a power factor deviation Δφ obtained bysubtracting the target value of the power factor from the power factorφpf output from the power factor calculator 217 to an amplitude/phaseregulator 224.

On the other hand, a target-frequency setting unit 219 outputs a targetangular frequency ω to an integrator 225, and the integrator 225integrates the target angular frequency ω to convert it to a referencephase φe0, and outputs the reference phase φe0 to the amplitude/phaseregulator 224.

The amplitude/phase regulator applies the first to the third controlmethods, and has a control unit that outputs voltage amplitude Vs forincreasing the amplitude of the voltage V when the phase difference Δφincreases narrowly, for example, an amplitude regulating function forchanging the amplitude gain by a variable-gain I regulator or PIregulator, and a control unit that outputs a phase amount φe forretarding the reference phase φe0 of the voltage V when the phasedifference Δφ increases greatly, for example, a phase regulatingfunction for fine-tuning the reference phase φe0 based on the output ofthe variable-gain I regulator or PI regulator.

A sine-wave generator 221 generates a sine wave having the voltageamplitude Vs and the phase amount φe output from the amplitude/phaseregulator 224 to output the sine wave to a positive terminal of acomparator 223. A triangular wave from a triangular wave generator 222is input to a negative terminal of the comparator 223. The comparator223 outputs a pulse-width modulation (PWM) control signal modulated bythe triangular wave to the drive circuit 213, and the drive circuit 213drives and controls the respective switching elements 202 to 207 tooutput the three-phase AC signal.

In the third embodiment, the voltage V is regulated to satisfy Equations(1) to (3) and synchronously operated by the amplitude regulatingfunction of the amplitude/phase regulator 224. Excessive stability isheld by directly controlling the phase by the phase regulating function,thereby enabling the operation at the time of velocity fluctuation, atthe time of load fluctuation, and at the time of startup. It is becausethe voltage phase calculator 215 and the current phase calculator 216can detect the phase on the real time basis that such a highly accuratesynchronous operation is possible. Further, highly accurate synchronousoperation control of the synchronous motor can be performed with asimple configuration, without requiring any complicated process such asposition estimation of the rotor of the synchronous motor.

Further, according to the control method and the controller, dependenceon the motor constant (winding reactance (Ld, Lq), induced voltageconstant, winding resistance, moment of inertia, and the like) islittle. Accordingly, time required for adaptability verification of thecontrol (matching of control characteristic) with respect to the motorconstant, which has been conventionally required for each type of themotor to be used, can be reduced, thereby enabling reduction ofoperation cost and simplification of change to another type of motor.

The voltage phase calculator 215 detects the actual three-phase voltageby providing the voltage detector 214. However, because the three-phasevoltage is determined based on the output from the bridge circuit, asshown in FIG. 12, the output phase of the sine-wave generator 221 can bedirectly used. In this case, the configuration of the voltage detector214 and the voltage phase calculator 215 is eliminated, thereby enablinga simpler configuration.

As shown in FIG. 13, the amplitude/phase regulator 224 shown in FIG. 11can be separated into an amplitude regulator 226 and a phase regulator227. The amplitude regulator 226 outputs the voltage amplitude Vsregulated so that the power factor deviation Δφ decreases to thesine-wave generator 221. The phase regulator 227 outputs a phaseregulated amount regulated so that the power factor deviation Δφdecreases to an adder 228, and the adder 228 outputs a phase amount φeobtained by adding the phase regulated amount to the reference phase φe0to the sine-wave generator 221.

Further, as shown in FIG. 14, the first control method can be applied toregulate only the amplitude of the voltage V so that the power factordeviation Δφ decreases. In this case, the phase regulator 227 and theadder 228 shown in FIG. 13 are not provided, thereby further simplifyingthe configuration. The reference phase φe0 from the integrator 225 isdirectly output to the sine-wave generator 221. The synchronous motorcontroller shown in FIG. 14 is preferable for control of the synchronousmotor having less velocity fluctuation and load fluctuation.

A fourth embodiment of the present invention is explained next. In thefourth embodiment, a synchronous operation can be performed with anoptimum power factor capable of increasing the power consumptionefficiency.

The driven state of the synchronous motor is uniquely determinedaccording to the power factor and the torque. Therefore, a tabledescribing a relationship between the driven state and an optimum powerfactor having high power consumption efficiency corresponding to thetorque is formed to set an optimum power factor, thereby enabling asynchronous operation matched with a driving purpose.

FIG. 15 depicts an optimum power factor characteristic having high powerconsumption efficiency when the torque is set as a parameter. The upperpart of FIG. 15 depicts a change of power factor with respect to achange of current Id, using the torque as the parameter, and the lowerpart of FIG. 15 depicts a change of current magnitude with respect to achange of current Id, using the torque as the parameter. From the upperpart of FIG. 15, it is seen that the range of the power factor φpf thatcan be taken is limited by the size of the torque. For example, with atorque of 1 Newton-meter (Nm), operations can be performed even if thepower factor φpf is set to a level of approximately less than 50degrees; however, when the torque is 10 Nm, operations cannot beperformed unless the power factor φpf is set to a level of approximatelyless than −30 degrees. That is, the power factor needs to be set,matched with the torque value.

The current magnitude in the lower part of FIG. 15 corresponds to aresistance loss. Therefore, the resistance loss becomes the smallest andthe power consumption efficiency becomes the largest, at a point wherethe current magnitude is the smallest. When a plurality of points P1 atwhich the power consumption efficiency becomes the largest is plotted aspoints P2 on the torque line corresponding to the upper part of FIG. 15,a maximum efficiency line L is obtained. That is, a relationship of thepower factor with respect to the torque where the power consumptionefficiency becomes the largest is obtained.

As shown in FIG. 16, therefore, a target-power-factor converter 229 isadded to the configuration shown in FIG. 11. The target-power-factorconverter 229 uses the table in which the relationship of the powerfactor with respect to the torque where the power consumption efficiencybecomes the largest is stored, to output the power factor, at which thepower consumption efficiency becomes the largest with respect to theinput torque, to the target-power-factor setting unit 218. The inputtorque can be calculated by monitoring voltages Vr, Vs, and Vt of theR-phase, S-phase, and T-phase detected by the voltage detector 214, andmonitoring currents Ir, Is, and It of the R-phase, S-phase, and T-phasedetected by the current detectors 208 to 210.

In the fourth embodiment, the voltage and the current of respectivephases are detected, to calculate the torque from the detected values,and the target value of the power factor is set, at which the powerconsumption efficiency becomes the largest with respect to thecalculated torque. Accordingly, synchronous operations can be performedwith excellent power consumption efficiency.

As described above, in the fourth embodiment, the target value of thepower factor is set, at which the power consumption efficiency becomesthe largest with respect to the torque. However, because the torque isinversely proportional to the angular frequency ω of the synchronousmotor, the angular frequency ω can be detected to set the target valueof the power factor, at which the power consumption efficiency becomesthe largest with respect to the torque, also taking the detected angularfrequency into consideration.

With the phase detection method and the phase detecting apparatusaccording to an aspect of the present invention, it is determined whichof a plurality of continuous sections having different magnitudecorrelation of signal amplitude of each phase the section is based on aninput signal amplitude value of a plurality of phases, predeterminedsubtraction is performed with respect to the signal amplitude betweenrespective phases for each determined section, to obtain a normalizedamplitude value normalized in the section, using the subtraction result,and the normalized amplitude value is converted to a vector phase forone cycle based on a predetermined phase, and the vector phase is outputcorresponding to the section determined at the section determinationstep. Accordingly, phase detection can be performed easily and highlyaccurately on the real time basis, without performing complicatedcalculation having a large load, such as an arctan operation.

Moreover, a voltage vector phase and a current vector phase to beapplied to the synchronous motor are obtained based on the phasedetection method or the phase detecting apparatus described above, tocalculate a power factor, which is a phase difference between thevoltage vector phase and the current vector phase on the real timebasis. Accordingly, synchronous operations of the synchronous motor canbe controlled with a simple configuration and with high accuracy.

Although the invention has been described with respect to specificembodiments for a complete and clear disclosure, the appended claims arenot to be thus limited but are to be construed as embodying allmodifications and alternative constructions that may occur to oneskilled in the art that fairly fall within the basic teaching herein setforth.

1. A synchronous-motor control method comprising: calculating a voltagevector phase and a current vector phase to be applied to the synchronousmotor based on a phase detection method to calculate a power factor,which is a phase difference between the voltage vector phase and thecurrent vector phase on a real time basis; and controlling thesynchronous motor based on the power factor, wherein the phase detectionmethod comprising: determining which of a plurality of continuoussections having different magnitude correlation of signal amplitude ofeach phase a section is, based on an input signal amplitude value of aplurality of phases; normalizing including performing predeterminedsubtraction with respect to the signal amplitude between respectivephases for each section determined at the determining, to obtain anormalized amplitude value normalized in the section, using thesubtraction result; and outputting including converting the normalizedamplitude value obtained at the normalizing to a vector phase for onecycle based on a predetermined phase, and outputting the vector phasecorresponding to the section determined at the determining.
 2. Thesynchronous-motor control method according to claim 1, furthercomprising feedback controlling including providing a target value ofthe power factor and performing feedback control so that the powerfactor is approximated to the target value.
 3. The synchronous-motorcontrol method according to claim 2, wherein at the feedbackcontrolling, amplitude adjustment is performed with respect to thevoltage amplitude value to be applied to the synchronous motor toapproximate the power factor to the target value.
 4. Thesynchronous-motor control method according to claim 2, wherein at thefeedback controlling, amplitude adjustment is performed for reducing anerror between the power factor and the target value, to approximate thepower factor to the target value.
 5. The synchronous-motor controlmethod according to claim 2, wherein at the feedback controlling, a gainof at least one of amplitude adjustment or phase adjustment is changedaccording to a torque of the synchronous motor obtained based on thevoltage value of each phase and the current value of each phase.
 6. Thesynchronous-motor control method according to claim 2, wherein thefeedback controlling further includes target-power-factor convertingincluding outputting a target value of the power factor corresponding tothe voltage value and the current value of each phase based on arelationship between the torque obtained based on the voltage value andthe current value of each phase and a power factor having high powerconsumption efficiency, wherein the feedback controlling is performed toapproximate the power factor to the target value, using the targetvalue.
 7. The synchronous-motor control method according to claim 6,wherein at the target-power-factor converting, the voltage value and thecurrent value of each phase are feedback controlled to output a targetvalue of the power factor having the high power consumption efficiencywith respect to the torque.
 8. The synchronous-motor control methodaccording to claim 1, wherein at the power-factor calculating, thevoltage vector phase to be applied to the synchronous motor is detectedbased on a drive control signal to be applied to the synchronous motor.9. A synchronous-motor control method comprising: calculating a voltagevector phase and a current vector phase to be applied to the synchronousmotor based on a phase detection method to calculate a power factor,which is a phase difference between the voltage vector phase and thecurrent vector phase on a real time basis; and controlling thesynchronous motor based on the power factor, wherein the phase detectionmethod comprising: determining which of six continuous sections, firstto sixth sections, in which magnitude correlation of a signal amplitudevalue of an input three-phase signal of R-phase, S-phase, and T-phasetakes a R-phase value>T-phase value>S-phase value, a R-phasevalue>S-phase value>T-phase value, a S-phase value>R-phase value>T-phasevalue, a S-phase value>T-phase value>R-phase value, a T-phasevalue>S-phase value>R-phase value, and a T-phase value>R-phasevalue>S-phase value, the section is; calculating the first section by((R-phase value)−(T-phase value))/((R-phase value)−(S-phase value)), thesecond section by ((S-phase value)−(T-phase value))/((R-phasevalue)−(T-phase value)), the third section by ((S-phase value)−(R-phasevalue))/((S-phase value)−(T-phase value)), the fourth section by((T-phase value)−(R-phase value))/((S-phase value)−(R-phase value)), thefifth section by ((T-phase value)−(S-phase value))/((T-phasevalue)−(R-phase value)), the sixth section by ((R-phase value)−(S-phasevalue))/((T-phase value)−(S-phase value)), to obtain a normalizedamplitude value normalized in each section; and second outputtingincluding multiplying the normalized amplitude value of the first to thesixth sections, respectively, by a phase of 60°, to calculate a phasevalue by adding phases of 30°, 90°, 150°, 210°, 270°, and 330°,respectively, to the multiplied values of the first to the sixthsections, and when the phase value of the sixth section is equal to orlarger than 360°, obtaining a phase value by subtracting the phase of360° from the phase value, and outputting a vector phase for one cycle.10. The synchronous-motor control method according to claim 9, furthercomprising feedback controlling including providing a target value ofthe power factor and performing feedback control so that the powerfactor is approximated to the target value.
 11. The synchronous-motorcontrol method according to claim 10, wherein at the feedbackcontrolling, amplitude adjustment is performed with respect to thevoltage amplitude value to be applied to the synchronous motor toapproximate the power factor to the target value.
 12. Thesynchronous-motor control method according to claim 10, wherein at thefeedback controlling, amplitude adjustment is performed for reducing anerror between the power factor and the target value, to approximate thepower factor to the target value.
 13. The synchronous-motor controlmethod according to claim 10, wherein at the feedback controlling, again of at least one of amplitude adjustment or phase adjustment ischanged according to a torque of the synchronous motor obtained based onthe voltage value of each phase and the current value of each phase. 14.The synchronous-motor control method according to claim 10, wherein thefeedback controlling further includes target-power-factor convertingincluding outputting a target value of the power factor corresponding tothe voltage value and the current value of each phase based on arelationship between the torque obtained based on the voltage value andthe current value of each phase and a power factor having high powerconsumption efficiency, wherein the feedback controlling is performed toapproximate the power factor to the target value, using the targetvalue.
 15. The synchronous-motor control method according to claim 14,wherein at the target-power-factor converting, the voltage value and thecurrent value of each phase are feedback controlled to output a targetvalue of the power factor having the high power consumption efficiencywith respect to the torque.
 16. The synchronous-motor control methodaccording to claim 9, wherein at the power-factor calculating, thevoltage vector phase to be applied to the synchronous motor is detectedbased on a drive control signal to be applied to the synchronous motor.17. A synchronous motor controller comprising: a voltage phase detectorthat acquires a vector phase of voltage to be applied to a synchronousmotor by a phase detecting apparatus; a current phase detector thatobtains a vector phase of current to be applied to the synchronous motorby the phase detecting apparatus; a power factor calculator thatcalculates a power factor, which is a phase difference between thevoltage vector phase detected by the voltage phase detector and thecurrent vector phase detected by the current phase detector, on a realtime basis; and a control unit that performs synchronous control on thesynchronous motor based on the power factor obtained by the power factorcalculator, wherein the phase detecting apparatus comprising: a sectiondetermining unit that determines which of a plurality of continuoussections having different magnitude correlation of signal amplitude ofeach phase a section is, based on an input signal amplitude value of aplurality of phases; an amplitude normalizing unit that performspredetermined subtraction with respect to the signal amplitude betweenrespective phases for each section determined by the section determiningunit, to obtain a normalized amplitude value normalized in the section,using the subtraction result; and a phase outputting unit that convertsthe normalized amplitude value obtained by the amplitude normalizingunit to a vector phase for one cycle based on a predetermined phase, andoutputs the vector phase corresponding to the section determined by thesection determining unit.
 18. The synchronous motor controller accordingto claim 17, further comprising a target-power-factor setting unit thatsets a target value of the power factor, wherein the control unitperforms feedback control to approximate the power factor obtained bythe power factor calculator to the target value set by thetarget-power-factor setting unit.
 19. The synchronous motor controlleraccording to claim 18, wherein the control unit performs amplitudeadjustment with respect to a voltage amplitude value to be applied tothe synchronous motor to approximate the power factor to the targetvalue.
 20. The synchronous motor controller according to claim 18,wherein the control unit performs phase adjustment for reducing an errorbetween the power factor calculated by the power factor calculator andthe target value, to approximate the power factor to the target value.21. The synchronous motor controller according to claim 18, wherein thecontrol unit changes a gain of at least amplitude adjustment or phaseadjustment is changed according to a torque of the synchronous motorobtained based on the voltage value of each phase and the current valueof each phase.
 22. The synchronous motor controller according to claim17, further comprising a target-power-factor converter that outputs atarget value of a power factor corresponding to the voltage value andthe current value of each phase based on a relationship between thetorque obtained based on the voltage value and the current value of eachphase and a power factor having high power consumption efficiency withthe torque, wherein the target-power-factor setting unit sets the powerfactor to the one output from the target-power-factor converter.
 23. Thesynchronous motor controller according to claim 22, wherein thetarget-power-factor converter feeds back the voltage value and thecurrent value of each phase to output a target value of the powerfactor.
 24. A synchronous motor controller comprising: a current phasedetector that acquires a vector phase of current to be applied to thesynchronous motor by a phase detecting apparatus; a power factorcalculator that calculates a power factor, which is a phase differencebetween a voltage vector phase and the current vector phase detected bythe current phase detector, on a real time basis; and a control unitthat performs synchronous control with respect to the synchronous motorbased on the power factor obtained by the power factor calculator,wherein the voltage vector phase to be input to the power factorcalculator is controlled by the control unit, so that the phase is aphase of a voltage drive signal for generating an AC signal to beapplied to the synchronous motor, wherein the phase detecting apparatuscomprising: a section determining unit that determines which of aplurality of continuous sections having different magnitude correlationof signal amplitude of each phase a section is, based on an input signalamplitude value of a plurality of phases; an amplitude normalizing unitthat performs predetermined subtraction with respect to the signalamplitude between respective phases for each section determined by thesection determining unit, to obtain a normalized amplitude valuenormalized in the section, using the subtraction result; and a phaseoutputting unit that converts the normalized amplitude value obtained bythe amplitude normalizing unit to a vector phase for one cycle based ona predetermined phase, and outputs the vector phase corresponding to thesection determined by the section determining unit.
 25. A synchronousmotor controller comprising: a voltage phase detector that acquires avector phase of voltage to be applied to a synchronous motor by a phasedetecting apparatus; a current phase detector that obtains a vectorphase of current to be applied to the synchronous motor by the phasedetecting apparatus; a power factor calculator that calculates a powerfactor, which is a phase difference between the voltage vector phasedetected by the voltage phase detector and the current vector phasedetected by the current phase detector, on a real time basis; and acontrol unit that performs synchronous control on the synchronous motorbased on the power factor obtained by the power factor calculator,wherein the phase detecting apparatus comprising: a section determiningunit that determines which of six continuous sections, first to sixthsections, in which magnitude correlation of a signal amplitude value ofan input three-phase signal of R-phase, S-phase, and T-phase takes aR-phase value>T-phase value>S-phase value, a R-phase value>S-phasevalue>T-phase value, a S-phase value>R-phase value>T-phase value, aS-phase value>T-phase value>R-phase value, a T-phase value>S-phasevalue>R-phase value, and a T-phase value>R-phase value>S-phase value,the section is; an amplitude normalizing unit that calculates the firstsection by ((R-phase value)−(T-phase value))/((R-phase value)−(S-phasevalue)), the second section by ((S-phase value)−(T-phasevalue))/((R-phase value)−(T-phase value)), the third section by((S-phase value)−(R-phase value))/((S-phase value)−(T-phase value)), thefourth section by ((T-phase value)−(R-phase value))/((S-phasevalue)−(R-phase value)), the fifth section by ((T-phase value)−(S-phasevalue))/((T-phase value)−(R-phase value)), the sixth section by((R-phase value)−(S-phase value))/((T-phase value)−(S-phase value)), toobtain a normalized amplitude value normalized in each section; and aphase outputting unit that multiplies the normalized amplitude value ofthe first to the sixth sections, respectively, by a phase of 60°, tocalculate a phase value by adding phases of 30°, 90°, 150°, 210°, 270°,and 330°, respectively, to the multiplied values of the first to thesixth sections, and when the phase value of the sixth section is equalto or larger than 360°, obtains a phase value by subtracting the phaseof 360° from the phase value, and outputs a vector phase for one cycle.26. The synchronous motor controller according to claim 25, furthercomprising a target-power-factor setting unit that sets a target valueof the power factor, wherein the control unit performs feedback controlto approximate the power factor obtained by the power factor calculatorto the target value set by the target-power-factor setting unit.
 27. Thesynchronous motor controller according to claim 26, wherein the controlunit performs amplitude adjustment with respect to a voltage amplitudevalue to be applied to the synchronous motor to approximate the powerfactor to the target value.
 28. The synchronous motor controlleraccording to claim 26, wherein the control unit performs phaseadjustment for reducing an error between the power factor calculated bythe power factor calculator and the target value, to approximate thepower factor to the target value.
 29. The synchronous motor controlleraccording to claim 26, wherein the control unit changes a gain of atleast amplitude adjustment or phase adjustment is changed according to atorque of the synchronous motor obtained based on the voltage value ofeach phase and the current value of each phase.
 30. The synchronousmotor controller according to claim 25, further comprising atarget-power-factor converter that outputs a target value of a powerfactor corresponding to the voltage value and the current value of eachphase based on a relationship between the torque obtained based on thevoltage value and the current value of each phase and a power factorhaving high power consumption efficiency with the torque, wherein thetarget-power-factor setting unit sets the power factor to the one outputfrom the target-power-factor converter.
 31. The synchronous motorcontroller according to claim 30, wherein the target-power-factorconverter feeds back the voltage value and the current value of eachphase to output a target value of the power factor.
 32. A synchronousmotor controller comprising: a current phase detector that acquires avector phase of current to be applied to the synchronous motor by aphase detecting apparatus; a power factor calculator that calculates apower factor, which is a phase difference between a voltage vector phaseand the current vector phase detected by the current phase detector, ona real time basis; and a control unit that performs synchronous controlwith respect to the synchronous motor based on the power factor obtainedby the power factor calculator, wherein the voltage vector phase to beinput to the power factor calculator is controlled by the control unit,so that the phase is a phase of a voltage drive signal for generating anAC signal to be applied to the synchronous motor, wherein the phasedetecting apparatus comprising: a section determining unit thatdetermines which of six continuous sections, first to sixth sections, inwhich magnitude correlation of a signal amplitude value of an inputthree-phase signal of R-phase, S-phase, and T-phase takes a R-phasevalue>T-phase value>S-phase value, a R-phase value>S-phase value>T-phasevalue, a S-phase value>R-phase value>T-phase value, a S-phasevalue>T-phase value>R-phase value, a T-phase value>S-phase value>R-phasevalue, and a T-phase value>R-phase value>S-phase value, the section is;an amplitude normalizing unit that calculates the first section by((R-phase value)−(T-phase value))/((R-phase value)−(S-phase value)), thesecond section by ((S-phase value)−(T-phase value))/((R-phasevalue)−(T-phase value)), the third section by ((S-phase value)−(R-phasevalue))/((S-phase value)−(T-phase value)), the fourth section by((T-phase value)−(R-phase value))/((S-phase value)−(R-phase value)), thefifth section by ((T-phase value)−(S-phase value))/((T-phasevalue)−(R-phase value)), the sixth section by ((R-phase value)−(S-phasevalue))/((T-phase value)−(S-phase value)), to obtain a normalizedamplitude value normalized in each section; and a phase outputting unitthat multiplies the normalized amplitude value of the first to the sixthsections, respectively, by a phase of 60°, to calculate a phase value byadding phases of 30°, 90°, 150°, 210°, 270°, and 330°, respectively, tothe multiplied values of the first to the sixth sections, and when thephase value of the sixth section is equal to or larger than 360°,obtains a phase value by subtracting the phase of 360° from the phasevalue, and outputs a vector phase for one cycle.